1. Field
Exemplary embodiments of the present invention relate to a delay circuit and, more particularly, to a delay circuit including a coarse delay line and a fine delay line.
2. Description of the Related Art
A delay circuit is a circuit that delays an input signal for a predetermined time and outputs a delayed signal in order to match signal timing. Since various semiconductor devices operate in synchronization with unique operation sequences and timing, delay circuits are used extensively in semiconductor devices.
FIG. 1 is a configuration diagram of a conventional delay circuit,
Referring to FIG, 1, the delay circuit includes a coarse delay line 110 and a fine delay line 120.
The coarse delay line 110 includes a plurality of coarse delay units (CDU) 110_1 to 110_10. Each of the coarse delay units 110_1 to 110_10 may have a large delay value. For example, each of the coarse delay units 110_1 to 110_10 may have a delay value of 10. Among the coarse delay units 110_1 to 110_10, the number of coarse delay units used to delay an input signal IN may be determined by coarse delay setting codes C_CODE<0:3>.
The fine delay line 120 includes a plurality of fine delay units (FDU) 120_1 to 120_10. Each of the fine delay units 120_1 to 120_10 may have a small delay value. For example, each of the fine delay units 120_1 to 120_10 may have a delay value of 1. Among the fine delay units 120_1 to 120_10, the number of fine delay units used to delay an input signal IN_F of the fine delay line 120 may be determined by fine delay setting codes F_CODE<0:3>.
The maximum delay value 10 of the fine delay line 120 is approximately equal to the delay value 10 of one of the coarse delay units 110_1 to 110_10. Accordingly the number of fine delay units used for delaying a signal in the fine delay line 120 and the number of coarse delay units used to delay a signal in the coarse delay line 110 are adjusted, so that the delay circuit may be set to have various delay values of 0 to 110.
In order to set the delay circuit to have one of the various delay values of 0 to 110, the maximum delay value of the fine delay line 120 should be approximately equal to the delay value of one of the coarse delay units 110_1 to 110_10. However, it is difficult to make the maximum delay value of the fine delay line 120 approximate the delay value of one of the coarse delay units 110_1 to 110_10 due to variables such as pressure, voltage, and temperature (PVT).